Environmental Assay Inc.
Indoor Air Quality (IAQ)
Its Characteristics and Content
Dust
Mold and Pollen
Air Quality
Volatile Organic Compounds
Combustion Products
Airflow Dynamics
Airborne Particulate Matter
Non-Viable (non-living) Particulates
Dust - With forced airflow devices, one needs to consider particulate matter. There
is a certain amount of atmospheric dust constantly airborne. It may approach
infinitesimally small dimensions, yet accumulation will occur, even under the
best conditions. One way to remove dust is with a vacuum cleaner. Most vacuum
cleaners are equipped with a porous paper filter/bag. This is a coarse filter
able to trap particulates of about 10 microns (10 x 1/1,000,000 of a Meter) or
greater. Smaller particulates go through the filter. This presents a problem,
as our nasal passages are able to trap particulates that are 5 microns or
greater. What happens then, is that a typical vacuum cleaner produces a storm
of dust that is immediately ingested into our lungs. Better vacuum cleaners can
be supplied with Allergy or HEPA filter for most efficient cleaning.
Air circulation and conditioning machines present similar problems. When installed,
they are generally provided with coarse fiberglass filters that are good at
trapping pencils and leaves. Air circulation in this fashion, without proper
filtration for particulate matter, will change a localized dust problem into a large
area problem. After a number of years, sufficient dirt
and dust accumulation occurs within the air ducts. This provides a food base
for mold growth (improving filtration afterwards will not accomplish its set
goal), possibly causing biological irritation whose cause is hard to pinpoint,
and a more expensive cleanup than simply replacing and throwing away a
disposable filter. Great improvement can be achieved by replacing such
filters with high efficiency units (from initial installation) that cost only a
small amount more.
Dust Mites - microscopic animals that thrive in dust, leave droppings that are
potent allergens. They are too minute to be stopped by coarse
filters in vacuums or air moving equipment. Attempts to reduce their abundance
with such coarse filtered devices simply ensure their abundance is more evenly
spread throughout. They feed on a mix of organic matter, partly human skin cells
that are normally shed, and animal dander. A carpeted area provides the best growth
environment for them, especially due to moisture retention within the carpet.
Animal Dander is a byproduct of natural animal shedding processes. It becomes
an environmental offender when indoors, if cleanliness is not maintained regularly
and meticulously. Even so, cat dander is particularly irritating because it remains
airborne, coats every piece of fabric within a structure, and removal of the cat
will not reduce the dander problem until many months later. Human dander falls into
the same category. That is, it is organic and will provide a food base for microscopic
organisms like mold, and bacteria.
Adapted from "Airborne Respiratory Diseases and Mechanical Systems for Control
of Microbes",
W. J. Kowalski, P.E. and William Bahnfleth, PhD, P.E.
Viable particulates encompass (respectively in increasing size) Viruses,
Bacteria, Mold and associated Spores, and Pollen. While viruses and bacteria are ever present,
staying in reasonably good health, despite their presence, is mainly a function of good personal
and domestic hygiene. Keeping a clean house is essential for good health. When dirt tumbleweeds
become visible on hard floors, it is time to clean (usually weekly). With carpeting, where dirt
can hide in the knap, there is a deceptive impression of cleanliness. However, simply walking will
liberate what is within the carpert and make it airborne, so weekly cleaning is a good idea too.
Molds are necessary agents of recycling and exist everywhere. They
slowly devour most surfaces they come in contact with, reducing them to their
basic chemical constituents. If the surface is inert, as in metal, then they
may simply feed off the dirt on its surface. Particularly attractive to mold
are surfaces containing cellulose. Cellulose is the main component of wood and
its derivatives, such as paper. Cellulose is also a structural rearrangement of
simple sugars that gives the assembly great structural strength. Decomposition
or attack by mold would then provide them with an attractive sugar base that is
an excellent source of food.
They thrive particularly well on moist surfaces. Modern dwellings are
outfitted with a plumbing infrastructure that penetrates many structural walls.
Any leak (however small) provides the proper environment for mold to colonize.
Inattention to the leak(s) for greater than 24 hours, promotes conditions appropriate
for rapid growth (amplification). Allowing ambient moisture content to rise
above 60% will provide similar favorable conditions for growth. Continued
favorable conditions can allow sequentially more aggressive species to manifest
themselves, possibly feeding off the dead mold colonies they replace. While
many species are allergenic, some species are toxigenic, mutagenic, and
carcinogenic. When molds colonize a favorable surface they produce a mycelia
that penetrates the surface, in some respects similar to a plant's root system. They
also produce outcroppings (similar to plant's trunks and branches) that produce spores. When
agitated, these spores easily become airborne. You should easily begin to see
that surface treatment of mold infestation on a porous surface is a cheap and incomplete
solution.
Pollens share some characteristics with molds, in that they are easily
airborne, and some are irritants. Allergy symptoms are common with many individuals
for one or more types of pollen.
Corrective measures for Viable particulates (primarily for mold and pollen)
include proper filtration as in the previous topic, moisture control, and Ultra
Violet Germicidal Irradiation (UVGI) air stream sterilization (for bacteria and viruses) where feasible.
Some of the filtration issues can be improved with standalone air filtration units.
Some of these even integrate UVGI. However, those who may need them most have then also imposed on them
additional EMF issues as all such appliance cordage are Unshielded.
Electrostatic Precipitators are Not recommended since while they initially filter very well, in a short
time the plates become fouled and then highly charged particulate are emitted from the device, possibly
causing eye, nose, throat, and lung irritation.
VOCs are aromatic or out-gas byproducts (dry-out evaporation) of many chemicals
in our "modern" environment. Paint for instance, is a liquid product
that is applied to surfaces for a certain color rendition. The emulsion within
the paint fluid coats the surface it is applied to, while the liquid
evaporates. The liquid is a mixture of many volatile compounds that can be
biological irritants.
Engineered woods, plywood and particleboard in particular, are made of wood
sheets or pieces that are glued together. The glues use a formaldehyde base
that evaporates and irritates lungs, throat, and other organs.
Plastics are usually produced with phthalates (plasticizers) to give them "that soft feel". Ever smell that "new car smell"? It is in part due to the phthalates evaporating, which also coat the inside of the windshield and cause a slightly opaque coating. Plasticizers can be as much as 50% of the material content of plastics. These evaporate and become biological irritants (try at home: place water in a polyethylene bottle and keep in storage for 4-6 months, then taste the water and its associated "plastic" flavor). Some plastic glasses can impart that plastic flavor in a matter of minutes! On a similar note, if you have water in a plastic bottle and allow it to freeze, you will find that when the ice melts and you try to drink it, it will have a trashy taste, due to some of the chemicals leaching into the liquid (try at home: place partially full plastic bottle in freezer overnight; take out and allow to thaw, then sample for taste). Plastics are encountered in furniture, kitchen utensils, office supplies, carpeting, clothing, and just about everything that can be manufactured. To add insult to injury, many carpets are treated with fungicides / pesticides, which volatilize into the indoor environment. In a new home, the out-gassing becomes a default contaminant of the breathable environment for many years, And if the owners immediately occupy the structure upon completion, they risk long term effects that last beyond the time they migrate to a new residence.
An engineered source of VOC pollutants is the
hot water boiler. As it heats the water, the elevated temperatures make any VOC
more volatile. When the water is sprayed in the process of washing dishes,
clothes, or showering / bathing, the VOCs become airborne. Water acquires these
VOCs from ground contamination and runoffs, as well as water treatment
processes. Chlorine and Fluorine, common water treatment chemicals, also become
airborne, and irritate.
In a tight dwelling, the buildup of pollutants can be dramatically quick. While
many domestic water supplies are reasonably clean, even trace amounts of
certain VOCs are sufficient to introduce biological influence. Whether public
or private, a domestic water supply is well worth sampling on a regular basis,
yearly or so. If certain unwanted water contaminants are identified, then
filtration or sterilization can be introduced.
In a public water supply system, Chlorine is a major concern. While doing its duty in killing undesired microbes, it is not needed for showering. Ever get eye irritation from hot water while showering? Thank the Chlorine. Coincidentally, in the interest of conservation there are showerheads available that produce a very efficient atomization of the water flow at a minimal flow rate. While good for conservation, this is also most efficient for volatilizing Chlorine and other aromatic compounds in the water supply. A good filter (usually an activated charcoal unit, changed regularly) will easily reduce / remove the chemical content. Usage of a moderate flow shower head that does not finely atomize water droplets will also be helpful.
Since a VOC source material may be solid, liquid, or gas (if VOCs are entrained
in the fresh air supply), their removal can be a filtration issue (if they are sought
to be removed BEFORE they enter the living environment), or it can be a neutralizing
/ removal issue (if they are sought to be removed AFTER they enter the living space).
Access to air / liquid entry paths will most likely determine which method is employed.
In a new home, there are many construction materials that emit copious amounts
of VOC out-gas. Exterior walls (essentially being airtight barriers) enclose
a few additional sources. While some advocate a home bake-out to substantially
reduce VOC emissions (because the present norm is to occupy a house immediately upon
completion), the positioning of certain materials beyond moisture barriers, will keep
them available as long-term low-level sources of VOCs. When a home bake-out is considered,
it is conducted immediately after construction, by raising the internal temperature to a
high level (85 degrees Fahrenheit / 30 degrees Celsius), and then rapidly ventilating the
structure. The cycle is repeated several times, forcing enhanced out-gassing and air
volume purging.
There should be NO VOC content in a healthy
environment, other than NATURAL emissions from such things as aromatic flowers,
wood, etc.
A typical domestic setting is provided with a heat source that feeds a forced
air or hydronic system. Most often, the furnace uses indoor air to feed the
fire. When the furnace initially fires, before the stack-effect (updraft) is
established, there is an initial surge of partially burned combustion products
in all directions. This will produce a "smell" of gas or oil within
the immediate living space, reminiscent of a leaky exhaust duct (in the case of
an oil furnace, the smell may permeate into wall structures causing a lingering oil
smell long after the furnace has stopped operating; even if the oil furnace is replaced
with a gas one, there may still be an oily smell). As the updraft
is developed, those combustion products are sucked back into the furnace and
exhausted outdoors. If there are competing sources of suction elsewhere, such
as a clothes dryer, or a bathroom or kitchen fan, those partially burned combustion
products can migrate elsewhere throughout the home. During this process, more air
needs to be available to feed the fire. A whole-house vacuum (or negative
pressure when compared to outdoors) is established, dragging outdoor air in
through window, door, and boundary wall imperfections. Standing near any of
these will create a sensation of a cold draft. This describes the operation of an
Open Combustion heat source. A conventional fireplace also fits this description.
This is both good and bad.
From an air quality perspective this is very good, as human and animal life
is Oxygen dependent, requiring a continuous fresh supply of air. It also can be very bad
if there are sources of pollution outdoors, because these would also enter the
living environment.
From a comfort standpoint, this uncontrolled air entry is bad because it
generally involves very low humidity levels. Personal comfort, as well as
reduction in microbial growth potential, is accomplished with humidity levels
between 40 - 60%. Wintertime climates can produce humidity levels well below
20%. This will produce problems keeping a healthy skin tone, as well as
breathing, and eye irritation problems.
The solution does NOT include making doors and windows tighter.
When a furnace and a wood fireplace are both provided, they will compete
for the same supply of fresh air. Trying to
start a fire in the fireplace while the furnace is ignited might prevent
establishing the updraft in the fireplace, bringing all the combustion products
indoors.
If the fireplace is not in use, and its stack is near the furnace's, the
exhaust can be recycled back indoors by the negative pressure, unless the
fireplace damper is very-tightly fitting (which they seldom are),
with serious consequences.
A partial remedy to the above is to provide an external source of air for
furnace (or fireplace) combustion. This concept is then known as Sealed
Combustion. Doing so will eliminate the indoor vacuum,
and will allow the establishing of a more controlled moisture level, reducing
many related complaints. However, it will present other challenges
relating to a fresh supply of air, as removing the indoor vacuum will allow
indoor-generated pollutants to build up, eventually reducing the comfort level.
One remedy; is to use plants to provide a fresh supply of Oxygen and moisture, as well as remove
VOC buildup. Although forced ventilation is many times faster in providing air
exchange, plants do it without noise, without costly installation, and with
pleasing NATURAL settings and aromas. If plants are used, the soil needs to be
replaced occasionally, and it should not be kept thoroughly wet, to preclude
mold colonization. An inexpensive soil moisture indicator will be quite useful
in this respect.
There should be NO Combustion Products in a
healthy environment.
Air is essential to life, in the immediate and long-term sense. We are Oxygen consumers, and air is generally composed of about 21% Oxygen. After air is exhaled, the Oxygen content has been reduced to about 17%, with an accompanying increase in Carbon Dioxide (CO2). Such a shift in concentration does not provide sufficient Oxygen to remain conscious. When outdoor in a Natural environment, there is random air movement, and continuous production of Oxygen by plant life, as long as it is daytime. In an indoor setting, we generally eliminate plant Oxygen production, have reduced airflow, and when there isn't sufficient flow we perceive a "stuffy" feeling. That is produced by the Oxygen depletion in our immediate vicinity. Both Oxygen content and distribution can then become problems. Indoor plants that are well cared for will produce Oxygen, replenishing our needs. Forced airflow will provide a dispersal of CO2, and supply Oxygen from what remains indoors.
It is not uncommon to find an expensive mansion with lots of gadgetry and controls, and during times when the heating or cooling system is not required, there is a minimum of air motion. Confort then is only possible with a local fan to maintain some air motion. Any central air circulation system should be set up to maintain a minimum of airflow at all times. This has the added benefit that any dust generated by normal activities will be routed to filtration and captured, providing for cleaner air to breathe.
During inclement weather, whether hot or cold, we spend much of our time
indoor. Typically this does Not include air exchange with the outdoor
environment, except when doors are used to exit or enter the structure. One
alternative is a Heat Recovery Ventilator or Heat Recovery Air Exchanger. This device exchanges air with
the outdoor environment, causing the two separate air paths to flow through a
heat exchanger, allowing for reduction of heat loss or gain.
Some Definitions
Electrostatic - any device that uses high DC/static voltages. In many cases this involves charging a moving particle, and then capturing it by electrostatic field attraction when it passes a structure of different charge level. If the voltage is too high, Ozone is produced. The smallest voltage required to draw an electric arc in open air is about 300 Volts. An exposed arc causes Ozone, so if the voltages used in any device go above 300, they are very likely to cause Ozone, which is aromatic.
MEL / Maximum Exposure Level - The level above which various regulatory bodies define that action needs to be taken to reduce the exposure level to prevent injury. This can vary from one agency to another. While the general healthy population can fare well up to MELs, those with a frail immune system stand to suffer harm long before the MEL level is reached.
Non-Viable - Inert, or not having any life of its own.
Open Combustion - a combustion device that uses the same airspace it is trying to heat, to draw air from for its combustion needs. Its operation causes a whole-house vacuum. A conventional fireplace fits this description, as well as most gas/oil furnaces.
Sealed Combustion - a combustion device that gets the air it needs for combustion from outside the living space. "Vent-less" does not mean the same thing. Read your device literature carefully!
Viable - having some ability (within itself) to reproduce.
VOC / Volatile Organic Compound - any material that aerosolizes (evaporates) when exposed
to air. The vapor pressure of the material in air is lower than that in the enclosed material, so
it evaporates, and can possibly be detected by occupants if it is aromatic. From the EPA viewpoint,
VOC is only a material that harms the high-altitude Ozone layer. So many materials that are true VOCs
are not characterized as such.
Why are recommended exposure limits thus?
------------------------------------------- ------------------------------------------- © 2007 Sal La Duca 792 Green St.
Environmental Assay Inc. / Sal La Duca
Building Biologist
BS, BBEC/BBEI, CIEC
FCC Licensed
Phillipsburg NJ 08865 USA
908-454-3965